Silicon precursors to make ultra low-K films with high mechanical properties by plasma enhanced chemical vapor deposition

ABSTRACT

A method for depositing a low dielectric constant film on a substrate is provided. The low dielectric constant film is deposited by a process comprising reacting one or more organosilicon compounds and a porogen and then post-treating the film to create pores in the film. The one or more organosilicon compounds include compounds that have the general structure Si—C X —Si or —Si—O—(CH 2 ) n —O—Si—. Low dielectric constant films provided herein include films that include Si—C X —Si bonds both before and after the post-treatment of the films. The low dielectric constant films have good mechanical and adhesion properties, and a desirable dielectric constant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 11/777,185, filed Jul. 12, 2007, which is hereinincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to the fabricationof integrated circuits. More particularly, embodiments of the presentinvention relate to a process for depositing low dielectric constantfilms for integrated circuits.

2. Description of the Related Art

Integrated circuit geometries have dramatically decreased in size sincesuch devices were first introduced several decades ago. Since then,integrated circuits have generally followed the two year/half-size rule(often called Moore's Law), which means that the number of devices on achip doubles every two years. Today's fabrication facilities areroutinely producing devices having 90 nm and even 65 nm feature sizes,and tomorrow's facilities soon will be producing devices having evensmaller feature sizes.

The continued reduction in device geometries has generated a demand forfilms having lower dielectric constant (k) values because the capacitivecoupling between adjacent metal lines must be reduced to further reducethe size of devices on integrated circuits. In particular, insulatorshaving low dielectric constants, less than about 4.0, are desirable.Examples of insulators having low dielectric constants include spin-onglass, fluorine-doped silicon glass (FSG), carbon-doped oxide, andpolytetrafluoroethylene (PTFE), which are all commercially available.

More recently, low dielectric constant organosilicon films having kvalues less than about 3.0 and even less than about 2.5 have beendeveloped. One method that has been used to develop low dielectricconstant organosilicon films has been to deposit the films from a gasmixture comprising an organosilicon compound and a compound comprisingthermally labile species or volatile groups and then post-treat thedeposited films to remove the thermally labile species or volatilegroups, such as organic groups, from the deposited films. The removal ofthe thermally labile species or volatile groups from the deposited filmscreates nanometer-sized voids in the films, which lowers the dielectricconstant of the films, as air has a dielectric constant of approximately1.

While low dielectric constant organosilicon films that have desirablelow dielectric constants have been developed as described above, some ofthese low dielectric constant films have exhibited less than desirablemechanical properties, such as poor mechanical strength, which rendersthe films susceptible to damage during subsequent semiconductorprocessing steps. Semiconductor processing steps which can damage thelow dielectric constant films include plasma-based etching processesthat are used to pattern the low dielectric constant films. Ashingprocesses to remove photoresists or bottom anti-reflective coatings(BARC) from the dielectric films and wet etch processes can also damagethe films.

Thus, there remains a need for a process for making low dielectricconstant films that have improved mechanical properties and resistanceto damage from subsequent substrate processing steps.

SUMMARY OF THE INVENTION

The present invention generally provides methods for depositing a lowdielectric constant film. In one embodiment, the method includesintroducing one or more organosilicon compounds into a chamber, whereinthe one or more organosilicon compounds comprise a compound having thegeneral structure:

wherein each R¹ has the general formula C_(n)H_(2n+1), OC_(n)H_(2n+1) orC_(n)H_(2n−1). In some embodiments, each R¹ is independently selectedfrom the group consisting of CH₃, CH═CH₂, H, and OH, and R² is selectedfrom the group consisting of (CH₂)_(a), C═C, C═C, C₆H₄, C═O, (CF₂)_(b),and combinations thereof, with a and b being independently 1 to 4. Insome embodiments, at most one silicon atom will be bonded to an oxygenatom. In some embodiments, the one or more organosilicon compoundscomprise a compound having the general structure:

wherein each R³ has the general formula C_(n)H_(2n+1), OC_(n)H_(2n+1),or C_(n)H_(2n−1). In some embodiments, each R³ is independently selectedfrom the group consisting of CH₃, OCH₃, OC₂H₅, CH═CH₂, H, and OH, and cand d are independently 1 to 4. The method also includes introducing aporogen into the chamber and reacting the one or more organosiliconcompounds and the porogen in the presence of RF power to deposit a lowdielectric constant film on a substrate in the chamber. The lowdielectric constant film is then post-treated to substantially removethe porogen from the low dielectric constant film. The post-treating maycomprise a UV, e-beam, or thermal annealing treatment. The post-treatedlow dielectric constant film comprises Si—C_(x)—Si bonds.

In another embodiment, a method for depositing a low dielectric constantfilm comprises introducing one or more organosilicon compounds into achamber, wherein the one or more organosilicon compounds comprises acompound having the general structure:

wherein each R⁵ has the general formula C_(n)H_(2n+1), OC_(n)H_(2n+1),or C_(n)H_(2n−1). In some embodiments, each R⁵ is independently selectedfrom the group consisting of CH₃, OCH₃, OC₂H₅, CH═CH₂, H, and OH, and eis 1 to 3. In other embodiments, the one or more organosilicon compoundscomprises a compound having the general structure

wherein each R⁶ has the general formula C_(n)H_(2n+1), OC_(n)H_(2n+1),or C_(n)H_(2n−1). In some embodiments, each R⁶ is independently selectedfrom the group consisting of CH₃, OCH₃, OC₂H₅, CH═CH₂, H, and OH, and fis 1 to 4. The method also includes introducing a porogen into thechamber and reacting the one or more organosilicon compounds and theporogen in the presence of RF power to deposit a low dielectric constantfilm on a substrate in the chamber. The low dielectric constant film isthen post-treated to substantially remove the porogen from the lowdielectric constant film. The post-treating may comprise a UV, e-beam,or thermal annealing treatment.

In an additional embodiment, a method for depositing a low dielectricconstant film comprises introducing one or more organosilicon compoundsinto a chamber, wherein the one or more organosilicon compoundscomprises bis(triethoxysilyl)methane, introducing a porogen into thechamber, reacting the one or more organosilicon compounds and theporogen in the presence of RF power to deposit a low dielectric constantfilm on a substrate in the chamber, and then post-treating the lowdielectric constant film to substantially remove the porogen from thelow dielectric constant film.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a flow diagram illustrating an embodiment of the invention.

FIG. 2 is a flow diagram illustrating another embodiment of theinvention.

FIG. 3 is a graph of the flow rates of the one or more organosiliconcompounds and the porogen according to an embodiment of the invention.

FIG. 4 is a FTIR of a post-treated low dielectric constant film providedaccording to embodiments of the invention.

DETAILED DESCRIPTION

The present invention provides a method of depositing a low dielectricconstant film. The low dielectric constant film comprises silicon,oxygen, and carbon. The film also comprises nanometer-sized pores. Thelow dielectric constant film has a dielectric constant of about 3.0 orless, preferably about 2.5 or less, such as between about 2.0 and 2.2.The low dielectric constant film may have an elastic modulus of at leastabout 6 GPa. The low dielectric constant film may be used as anintermetal dielectric layer, for example. A method of depositing a lowdielectric constant film according to an embodiment of the inventionwill be described briefly with respect to FIG. 1 and then furtherdescribed below.

FIG. 1 is a process flow diagram summarizing an embodiment of theinvention. In step 102, one or more organosilicon compounds areintroduced into a chamber. The one or more organosilicon compoundscomprise a compound having the general structure —Si—C_(x)—Si—, whereinx is between 1 and 4 or the general structure —Si—O—(CH₂)_(n)—O—Si—,wherein n is between 1 and 4. In step 104, a porogen is introduced intothe chamber. In step 106, the one or more organosilicon compounds andthe porogen are reacted in the presence of RF power to deposit a lowdielectric constant film on a substrate in the chamber. In step 108, thelow dielectric constant film is post-treated to substantially remove theporogen from the low dielectric constant film.

The chamber into which the one or more organosilicon compounds and theporogen are introduced may be a plasma enhanced chemical vapordeposition (PECVD) chamber. The plasma for the deposition process may begenerated using constant radio frequency (RF) power, pulsed RF power,high frequency RF power, dual frequency RF power, or combinationsthereof. An example of a PECVD chamber that may used is a PRODUCER®chamber, available from Applied Materials, Inc. of Santa Clara, Calif.However, other chambers may be used to deposit the low dielectricconstant film.

Returning to step 102, the compound having the general structure—Si—C_(x)—Si— includes compounds that have the general structure:

wherein each R¹ has the general formula C_(n)H_(2n+1), OC_(n)H_(2n+1),or C_(n)H_(2n−1). In some embodiments, at least one R¹ comprises carbon.In other embodiments, at most one of the R¹ groups is a methylsilanogroup. In some embodiments, R¹ is independently selected from the groupconsisting of CH₃, OCH₃, OC₂H₅, CH═CH₂, H, and OH, and R² is selectedfrom the group consisting of (CH₂)_(a), C═C, C≡C, C₆H₄, C═O, (CF₂)_(b),and combinations thereof, with a and b being 1 to 4. In someembodiments, at most one silicon atom is bonded to an oxygen atom. Insome embodiments, the compound having the general structure—Si—C_(x)—Si— includes compounds that have the general structure:

wherein each R³ has the general formula C_(n)H_(2n+1), OC_(n)H_(2n+1),or C_(n)H_(2n−1). In some embodiments, each R³ is independently selectedfrom the group consisting of CH₃, OCH₃, OC₂H₅, CH═CH₂, H, and OH, and cand d are independently 1 to 4. As defined herein, values for R groupsand other groups that are independently selected may be the same ordifferent than the other groups. In some embodiments, the compoundhaving the general structure —Si—C_(x)—Si— is a poly-silanoalkane.

An example of a compound having the general structure:

is bis(triethoxysilano)methane (C₁₃H₃₂O₆Si₂).

An example of a compound having the general structure:

is tetramethyl-1,3-disilacyclobutane (C₆H₁₆Si₂).

Other compounds that have the general structure —Si—C_(x)—Si— includecompounds that have the general structure:

wherein each R⁵ has the general formula C_(n)H_(2n+1), OC_(n)H_(2n+1),or C_(n)H_(2n-1). In some embodiments, each R⁵ is independently selectedfrom the group consisting of CH₃, OCH₃, OC₂H₅, CH═CH₂, H, and OH, and eis 1 to 3. An example of such a compound istetramethyl-2,5-disila-1-oxacyclopentane or tetramethyldisilafuran(C₆H₁₆OSi₂).

The one or more organosilicon compounds having the general structure—Si—O—(CH₂)_(n)—O—Si—may comprise compounds having the structure

wherein each R⁶ has the general formula C_(n)H_(2n+1), OC_(n)H_(2n+1),or C_(n)H_(2n−1). In some embodiments, each R⁶ is independently selectedfrom the group consisting of CH₃, OCH₃, OC₂H₅, CH═CH₂, H, and OH, and fis 1 to 4. An example of such a compound is bis(trimethylsiloxy)ethane(C₈H₂₂O₂Si₂).

By using organosilicon compounds that comprise Si—C_(x)—Si bonds and theprocessing conditions described herein, low dielectric constant filmsthat comprise Si—C_(x)—Si bonds (with x being between 1 and 4) bothbefore and after post-treatment may be obtained. Depending on theorganosilicon compounds used, the films may also comprise Si—O—Si bonds.Films comprising Si—C_(x)—Si bonds are desirable, as it has beenobserved that films with high Si—C_(x)—Si/Si—CH₃ ratios have improvedashing resistance, adhesion, and thermal conductivity propertiescompared to films having more Si—CH₃ bonds.

The one or more organosilicon compounds may also comprise organosiliconcompounds that do not include the general structures described above.For example, the one or more organosilicon compounds may includemethyldiethoxysilane (MDEOS), tetramethylcyclotetrasiloxane (TMCTS),octamethylcyclotetrasiloxane (OMCTS), trimethylsilane (TMS),pentamethylcyclopentasiloxane, hexamethylcyclotrisiloxane,dimethyldisiloxane, tetramethyldisiloxane, hexamethyldisiloxane (HMDS),1, 3-bis(silanomethylene)disiloxane, bis(1-methyldisiloxanyl)methane,bis(1-methyldisiloxanyl)propane, hexamethoxydisiloxane (HMDOS),dimethyldimethoxysilane (DMDMOS), or dimethoxymethylvinylsilane (DMMVS).

Returning to step 104, the porogen is a compound that comprisesthermally labile groups. The thermally labile groups may be cyclicgroups, such as unsaturated cyclic organic groups. The term “cyclicgroup” as used herein is intended to refer to a ring structure. The ringstructure may contain as few as three atoms. The atoms may includecarbon, nitrogen, oxygen, fluorine, and combinations thereof, forexample. The cyclic group may include one or more single bonds, doublebonds, triple bonds, and any combination thereof. For example, a cyclicgroup may include one or more aromatics, aryls, phenyls, cyclohexanes,cyclohexadienes, cycloheptadienes, and combinations thereof. The cyclicgroup may also be bi-cyclic or tri-cyclic. In one embodiment, the cyclicgroup is bonded to a linear or branched functional group. The linear orbranched functional group preferably contains an alkyl or vinyl alkylgroup and has between one and twenty carbon atoms. The linear orbranched functional group may also include oxygen atoms, such as in aketone, ether, and ester. The porogen may comprise a cyclic hydrocarboncompound. Some exemplary porogens that may be used include norbornadiene(BCHD, bicycle(2.2.1)hepta-2,5-diene), alpha-terpinene (ATP),vinylcyclohexane (VCH), phenylacetate, butadiene, isoprene,cyclohexadiene, 1-methyl-4-(1-methylethyl)-benzene (cymene), 3-carene,fenchone, limonene, cyclopentene oxide, vinyl-1,4-dioxinyl ether, vinylfuryl ether, vinyl-1,4-dioxin, vinyl furan, methyl furoate, furylformate, furyl acetate, furaldehyde, difuryl ketone, difuryl ether,difurfuryl ether, furan, and 1,4-dioxin.

As shown in step 106, the one or more organosilicon compounds and theporogen are reacted in the presence of RF power to deposit a lowdielectric constant film on a substrate in the chamber. One or moreporogens may be reacted with the one or more organosilicon compounds.The porogen reacts with the one or more organosilicon compounds todeposit a film that retains the thermally labile groups therein.Post-treating the film, as described in step 108, results in thedecomposition and evolution of the porogens and/or the thermally labilegroups from the film, resulting in the formation of voids ornanometer-sized pores in the film.

The one or more organosilicon compounds may be introduced into thechamber at a flow rate between about 10 mgm and about 5000 mgm. Theporogen may be introduced into the chamber at a flow rate between about10 mgm and about 5000 mgm. Optionally, an oxidizing gas, such as O₂,N₂O, CO₂, or combinations thereof, may be introduced into the chamber ata flow rate between about 0 sccm and about 10000 sccm and reacted withthe one or more organosilicon compounds and the porogen. A dilution orcarrier gas, such as helium, argon, or nitrogen, may also be introducedinto the chamber at a flow rate between about 10 sccm and about 10000sccm.

The flow rates described above and throughout the instant applicationare provided with respect to a 300 mm chamber having two isolatedprocessing regions, such as a PRODUCER® chamber, available from AppliedMaterials, Inc. of Santa Clara, Calif. Thus, the flow rates experiencedper each substrate processing region are half of the flow rates into thechamber.

Although the introduction of the one or more organosilicon compounds andthe introduction of the porogen into the chamber are shown sequentiallyas steps 102 and 104, the introduction of the one or more organosiliconcompounds and the introduction of the porogen may be performedsimultaneously. However, in a preferred embodiment, the one or moreorganosilicon compounds are introduced into the chamber before theporogen. In this embodiment, the one or more organosilicon compounds areintroduced into the chamber at a first flow rate and then ramped up to asecond flow rate. The porogen is introduced into the chamber at a thirdflow rate and then ramped up to a fourth flow rate. The one or moreorganosilicon compounds are ramped up to the second flow rate before theporogen is ramped up to the fourth flow rate.

FIG. 2 is a process flow diagram illustrating a method of depositing alow dielectric constant film according to an embodiment in which the oneor more organosilicon compounds are introduced into the chamber beforethe porogen. In step 201, a substrate is positioned on a substratesupport in a processing chamber capable of performing PECVD. In step203, a gas mixture having a composition including one or moreorganosilicon compounds and optionally one or more oxidizing gases isintroduced into the chamber through a gas distribution plate of thechamber, such as a showerhead. A radio-frequency (RF) power is appliedto an electrode, such as the showerhead, in order to provide plasmaprocessing conditions in the chamber. The gas mixture is reacted in thechamber in the presence of RF power to deposit an initiation layercomprising a silicon oxide layer that adheres strongly to the underlyingsubstrate.

In step 205, the flow rate of the one or more organosilicon compounds isincreased at a ramp-up rate between about 100 mg/min/sec and about 5000mg/min/sec, preferably, between about 1000 mg/min/sec and about 2000mg/min/sec, in the presence of the RF power, to deposit a firsttransition layer until reaching a predetermined organosilicon compoundgas mixture. The ramp-up of the flow rate conditions is performed suchthat variation in DC bias of the gas distribution plate is less than 60volts, preferably less than 30 volts, to avoid plasma induced damage(PID).

In step 207, while keeping the predetermined organosilicon compound gasmixture constant, a gas mixture having a composition including a porogenis introduced into the chamber through the gas distribution plate. Instep 209, the flow rate of the porogen is increased at a ramp-up ratebetween about 100 mg/min/sec and about 5000 mg/min/sec, preferably,between about 200 mg/min/sec and about 1000 mg/min/sec, to deposit asecond transition layer until reaching a predetermined final gasmixture.

In step 211, the predetermined final gas mixture, i.e., the final gasmixture having a composition including the one or more organosiliconcompounds and the porogen, is reacted in the chamber in the presence ofRF power to deposit a final layer that is a low dielectric constantfilm. Upon completion of the deposition, the RF power is terminated. Thechamber pressure is maintained during the RF power termination, such asby not opening the chamber throttle valve. Not wishing to be bound bytheory, it is believed that by separating the ramp-up rates of theorganosilicon compounds and the porogen compound, a more stable andmanufacturable process can be obtained, yielding dielectric films withless defect issues, such as particle adders.

In step 213, the low dielectric constant film is post-treated tosubstantially remove the porogen from the low dielectric constant film.

FIG. 3 is a graph illustrating the flow rates of the one or moreorganosilicon compounds and the porogen versus time according to anembodiment of the invention. The gas mixture having a compositionincluding one or more organosilicon compounds and optionally one or moreoxidizing gases is introduced into the chamber to deposit an initiationlayer, as described above with respect to step 203 of FIG. 2. Theinitiation layer deposition may have a time range of between about 1second and about 10 seconds.

The flow rate of the one or more organosilicon compounds is thenincreased at the ramp-up rate to deposit a first transition layer untilreaching a predetermined organosilicon compound gas mixture, asdescribed above with respect to step 205 of FIG. 2. The first transitionlayer deposition may have a time range of between about 1 second andabout 10 seconds.

While keeping the predetermined organosilicon compound gas mixtureconstant, a gas mixture having a composition including one or moreporogen compounds is introduced into the chamber, and the flow rate ofthe one or more porogen compounds is increased at a ramp-up rate todeposit a second transition layer until reaching a predetermined finalgas mixture, as described above with respect to step 209 of FIG. 2. Thesecond transition layer deposition may have a time range of betweenabout 1 second and about 180 seconds.

The predetermined final gas mixture having a composition including theone or more organosilicon compounds and the porogen is reacted in thechamber in the presence of RF power to deposit a final layer that is alow dielectric constant film, as described above with respect to step211 of FIG. 2. The final layer deposition may have a time range ofbetween about 15 seconds and about 180 seconds.

It is believed that the initiation sequence for the deposition of thelow dielectric constant film described above with respect to FIGS. 2 and3 improves the adhesion of the low dielectric constant film to theunderlying layer on the substrate on which it is deposited by providingimproved control of the porosity and carbon content of the lowdielectric constant film at the interface between the low dielectricconstant film and the underlying layer.

Returning to step 106 of FIG. 1, during the reaction of the one or moreorganosilicon compounds and the porogen to deposit the low dielectricconstant film on the substrate in the chamber, the substrate istypically maintained at a temperature between about 100° C. and about400° C. The chamber pressure may be between about 1 Torr and about 20Torr, and the spacing between a substrate support and the chambershowerhead may be between about 200 mils and about 1500 mils. A powerdensity ranging between about 0.14 W/cm² and about 2.8 W/cm², which is aRF power level of between about 100 W and about 2000 W for a 300 mmsubstrate, may be used. The RF power is provided at a frequency betweenabout 0.01 MHz and 300 MHz, such as about 13.56 MHz. The RF power may beprovided at a mixed frequency, such as at a high frequency of about13.56 MHz and a low frequency of about 350 kHz. The RF power may becycled or pulsed to reduce heating of the substrate and promote greaterporosity in the deposited film. The RF power may also be continuous ordiscontinuous.

After the low dielectric constant film is deposited, the film ispost-treated, as described in step 108. Post-treatments that may be usedinclude electron beam (e-beam) treatments, ultraviolet (UV) treatments,thermal annealing treatments (in the absence of an electron beam and/orUV treatment), and combinations thereof.

Exemplary UV post-treatment conditions that may be used include achamber pressure of between about 1 Torr and about 10 Torr and asubstrate support temperature of between about 350° C. and about 500° C.The UV radiation may be provided by any UV source, such as mercurymicrowave arc lamps, pulsed xenon flash lamps, or high-efficiency UVlight emitting diode arrays. The UV radiation may have a wavelength ofbetween about 170 nm and about 400 nm, for example. Further details ofUV chambers and treatment conditions that may be used are described incommonly assigned U.S. patent application Ser. No. 11/124,908, filed onMay 9, 2005, which is incorporated by reference herein. The Nanocure™chamber from Applied Materials, Inc., is an example of a commerciallyavailable chamber that may be used for UV post-treatments.

Exemplary electron beam conditions that may be used include a chambertemperature of between about 200° C. and about 600° C., e.g. about 350°C. to about 400° C. The electron beam energy may be from about 0.5 keVto about 30 keV. The exposure dose may be between about 1 μC/cm² andabout 400 μC/cm². The chamber pressure may be between about 1 mTorr andabout 100 mTorr. The gas ambient in the chamber may be any of thefollowing gases: nitrogen, oxygen, hydrogen, argon, a blend of hydrogenand nitrogen, ammonia, xenon, or any combination of these gases. Theelectron beam current may be between about 0.15 mA and about 50 mA. Theelectron beam treatment may be performed for between about 1 minute andabout 15 minutes. Although any electron beam device may be used, anexemplary electron beam chamber that may be used is an Ebk™ electronbeam chamber available from Applied Materials, Inc. of Santa Clara,Calif.

An exemplary thermal annealing post-treatment includes annealing thefilm at a substrate temperature between about 200° C. and about 500° C.for about 2 seconds to about 3 hours, preferably about 0.5 to about 2hours, in a chamber. A non-reactive gas such as helium, hydrogen,nitrogen, or a mixture thereof may be introduced into the chamber at arate of about 100 to about 10,000 sccm. The chamber pressure ismaintained between about 1 mTorr and about 10 Torr. The preferredsubstrate spacing is between about 300 mils and about 800 mils.

The following examples illustrate embodiments of the invention. Thesubstrates in the examples were 300 mm substrates. The low dielectricconstant films were deposited on the substrates in a PRODUCERS chamberavailable from Applied Materials, Inc. of Santa Clara, Calif. and UVtreated in a Nanocure™ chamber available from Applied Materials, Inc. ofSanta Clara, Calif.

EXAMPLE 1

A low dielectric constant film was deposited on a substrate at about 7.5Torr and a temperature of about 300° C. The spacing was 300 mils, andthe RF power was provided at 300 W at 13.56 MHz. The followingprocessing gases and flow rates were used: bis(triethoxysilyl)methane at2000 mgm, norbornadiene at 300 mgm, helium at 1500 sccm. The film wasthe post-treated with a UV treatment. After the post-treatment, the filmhad a refractive index of 1.3702, a dielectric constant of 2.44, anelastic modulus of 9.1 GPa, a hardness of 1.2 GPa, and a shrinkage of9.8%.

EXAMPLE 2

A low dielectric constant film was deposited on a substrate at about 7.5Torr and a temperature of about 225° C. The spacing was 400 mils, andthe RF power was provided at 450 W at 13.56 MHz. The followingprocessing gases and flow rates were used: bis(triethoxysilyl)methane at500 mgm, alpha-terpinene at 2000 mgm, methyldiethoxysilane at 500 mgm,oxygen at 50 sccm, and helium at 3500 sccm. The film was thepost-treated with a UV treatment. After the post-treatment, the film hada refractive index of 1.3443, a dielectric constant of 2.51, an elasticmodulus of 11.1 GPa, a hardness of 1.6 GPa, and a shrinkage of 15.70%.

FIG. 4 shows the results of FTIR analysis performed on the lowdielectric constant film of Example 1 after the UV treatment. The FTIRanalysis shows that the Si—C—Si bonding (Si—C—Si peak at 1630 cm⁻¹)provided by the organosilicon compound bis(triethoxysilyl)methane ispreserved in the post-treated film, and thus, the post-treated film hasa desirable Si—C—Si network structure.

It was also found that using precursors with Si—C—Si bonds to obtainfilms with higher Si—C—Si/SiCH₃ ratios also resulted in films havingsmaller pore sizes after post-treatment than other films have similardielectric constants and lower Si—C—Si/SiCH₃ ratios. Films with smallerpore sizes are desirable as they are stronger and less likely to bedamaged during further processing than films with larger pore sizes.

It is recognized that the organosilicon compounds provided herein can beused in gas mixtures that do not contain a porogen to chemically vapordeposit low dielectric constant films. However, while films depositedfrom gas mixtures that comprise the organosilicon compounds describedherein and lack a porogen are expected to have improved mechanicalproperties compared to films deposited from porogen-free mixturescomprising other organosilicon compounds, typically, a porogen isincluded to provide the desired, lower dielectric constants of about 2.4or less.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method of depositing a low dielectric constant film, comprising:introducing one or more organosilicon compounds into a chamber, whereinthe one or more organosilicon compounds comprises a compound having thegeneral structure:

wherein each R⁵ is independently selected from the group consisting ofCH₃, CH═CH₂, OCH₃, OC₂H₅, H, and OH, and e is 1 to 3; introducing aporogen into the chamber; reacting the one or more organosiliconcompounds and the porogen in the presence of RF power to deposit a lowdielectric constant film on a substrate in the chamber; and thenpost-treating the low dielectric constant film to substantially removethe porogen from the low dielectric constant film.
 2. The method ofclaim 1, wherein the post-treated low dielectric constant film comprisesSi—C_(x)—Si bonds, wherein x is 1 to
 4. 3. The method of claim 1,wherein the one or more organosilicon compounds comprisestetramethyl-2,5-disila-1-oxacyclopentane or tetramethyldisilafuran. 4.The method of claim 1, wherein introducing the one or more organosiliconcompounds into the chamber comprises introducing the one or moreorganosilicon compounds at a first flow rate and ramping up to a secondflow rate, introducing the porogen into the chamber comprisesintroducing the porogen at a third flow rate and ramping up to a fourthflow rate, and the one or more organosilicon compounds are ramped up tothe second flow rate before the porogen is ramped up to the fourth flowrate.
 5. The method of claim 4, wherein the post-treating comprises aUV, e-beam, or thermal annealing treatment.
 6. The method of claim 4,wherein the porogen comprises a cyclic hydrocarbon compound.